Downloading windows 7 for free

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but make sure that it's available for 90 days trial period only.
Following Link contains download link for Windows 7, this link is redirecting to India study channel

Check this link: Windows 7 free trial version for download

advantage of using USB

USB has got many advantage over other type of ports being used in PC's like serial and parallel.
User is having a very good rewarding and productive experience.

• Easy to use: It's easy to use, just simply plug-in and start using any device with PC. Simply "Plug and Play". Just connect disconnect and reconnect any device without rebooting PC.

• High Speed: It has speed of around 12Mbits/sec, which is around 100 times faster than serial ports. and with USB 2.0 specifications speed of 480 Mbits/s will be available.

• Expandable: Normally PC's come with 2 or 4 USB ports, which can be extended for use upto 127 ports using USB hubs.

• Reduced Size: Size of USB port is quite small than Serial ports and Parallel Ports.

Adding peripherals to PC using USB is so easy that anyone can connect. USB has replaced all different kinds of serial and parallel port with just only one type of port that's "USB". No need of add-in Cards, DIP switch settings or don't need to restart PC. 

Since most of PC's come with 2 USB ports, so you can connect any extra device using a peripheral USB HUB which have additional ports and let you daisychain multiple device at a time.

Using USB you can have two way communication, which means you can use your PC to control the connected device like synchronizing  contacts, media files etc.

What is COM Port? What is Serial Port? What is relation between COM and serial Port?

COM Port(Communication Port) is the original name given to serial ports on IBM compatible computers.
A serial port is asynchronous port on computer used to connect a serial device to computer capable of transmitting 1 bit at a time. It's basically a I/O port to get the data in and out of using computer. Normally every PC has one or 2 COM ports(serial ports).
A keyboard may be connected to COM1 and some other device may be connected to COM2.
Serial ports were mostly used for communication with RS-232, RS-485 system. A serial port is more than just a port, it converts data from parallel to serial and changes its electrical representation. Inside computer data flows in parallel( using many wires at a time) while serial flow is flow of bits over single wire.

Most of the electronics for serial port (convert parallel data to serial) is done in a computer chip that's known as UART.
Connectors for serial ports are of MALE and FEMALE type.

                                                       MALE JACK          Female JACK
Reference:
http://www.thaiio.com/serialportinfo.html

Universal Serial Bus

USB: USB stands for Universal Serial Bus.USB started in late 1990's( around 1996). USB is a hardware interface with defined protocols that enable Host computer to connect to different peripheral devices attached . It connects to a variety of devices like keyboard, mouse, printer, camera, pendrive, external HDD, etc. Hence for many of these kind of devices, USB has become common to have.
Design for USB is standardized by USB Implementers Forum or USB-IF. Currently one Host controller can support at max of 127 device at a time.
Initially when USB was started it was called as 1.0 with data rate of 12 Mbit/s but currently the USB we are using is USB 2.0 with data rate of 480 Mbit/sec. USB 2.0 was started in 2000
Features:

• USB provides Hot plugging and Hot swapping facility, which means you can add or remove peripherals without rebooting your PC or computer(Host controller).
• USB can also supply power to some of the devices which draw small amount of power like Pen Drive, mouse, keyboard.
• speed upto 480 Mbits/sec
• USB 2.0 can have max length of cable up to 5 meters and maximum hubs in series can be only 5.
• Data Cable for USB 2.0 use twisted pair to reduce noise and crosstalk.
• The USB 2.0 specifications provide a 5 V supply on a single wire from which connected USB devices may draw power. 
• Devices may be low powered, high powered, or self powered.

 Now a little bit of deep insight into USB.
To get USB working, you need Hardware and Software:
USb Hardware:                                     

HOST controller/Root HUB         
HUB
Device

USB Software:
Device Drivers
Drivers
Controller driver

Physical connection occurs between HOST controller and client bus interface( root hub) USB Host controllers are of following type:
Universal Host Controller Interface(UHCI)
Open Host Controller Interface(OHCI)
Enhanced Host Controller(EHCI)

USB Devices are of three types:
High speed:High speed devices see only high speed transactions, full or low speed devices are accessed via high speed split transactions.

Full Speed: Maximum data rate of 12 Mb/s
Low speed: These are limited in throughput(1.5 Mb/s) and also in feature.

USB connectors are of two types: Type A and type B
Type "A" connector supplies power and "B" receives power. Hence protecting users from connecting same type of connectors, same type of connectors can never be connected. Generally Type "A" connectors are used Host and Type B is used in devices.

Perl Programming

Perl is a programming language which can be used for a large variety of tasks.
Programs written in Perl are called Perl scripts, whereas the term the perl program refers to the system program named perl for executing Perl scripts.


There is a lot to learn in perl, but here I will mention only few items.

Data Types in Perl: scalars, arrays, associative arrays are some of the main data types.

Scalars: are used to store single value, or a string, and they are prefixed with $ sign. Perl doesn't differentiate between integers and floats like C does.

$price=25.6;
$name="Gaurav Gupta"

Array: It is similar to array in C/C++. It's generally called list in perl. It contains many scalar variables in form of list. It is prefixed with @ sign
@name=("gaurav", "kumar", "gupta", "5")

Associative array in perl is called as HASH, it's basically pairs of arrays

Difference between POP and IMAP protocols used for mail clients

POP and IMAP are protocols used at receiving end. POP is older than IMAP and has proved itself but IMAP being newer is also doing great.

POP is called as "POST OFFICE PROTOCOL", it lets you download mails from mail server to your computer or mobile, so that you can access your mail later with any program like outlook express, outlook 2003, windows mail etc... even when there is no internet connection because mails are downloaded to your system. but problem with it is that whenever it connects to server it downloads all mails and deletes contents from server.

IMAP is called as Internet Message Access Protocol(IMAP). It again download mails to your system, which can be accessed later even when you are not connected to net. Whenevr it connects it only reads all the mails on server or download header only, and download only mails which user wants to read.

Now the point comes of difference:
1. The main difference is IMAP keeps constant connection between mail server and mail clients(Computer/mobile). Which means if you perform any action on either system/client or Mail server, it appears on other side too.
Suppose you create a folder "personal" on client side then same folder will also appear on you mail server and vice versa.
Similarly if you move any message from Inbox to other folder in your mail server that will be reproduced in your mail client also. Overall you can say it has better SYNCING method over POP.

2. IMAP has feature of idle mode. Once you login to server you wouldn't be disconnected until you logout, which provides real time notification of mails. While with POP account it only reads mail, and disconnects so you will have to check your Inbox again for new mail.

3.With POP account only mails under ALL MAILs or INBOX are downloaded, not from spam or Deleted mails folder.

4. POP is better when you using for only one system, while IMAP will be better if having multiple systems to access mails.

So overall IMAP is the best way for configuring your mail accounts, because you won't have to worry about maintaining folders over separate places.

IMAP provides better way to access your mailbox from multiple devices, you can check new mails either from computer, mobile, or laptop...

So Finally I will suggest all of you to use IMAP account which is better, simpler, and easy to use for all.

Check this link for creation of Gadget

Hi,
Please check this link for learning to develop your own gadget:
http://code.google.com/apis/gadgets/
Gadgets are some simple JAVA script applications which can be embedded on webpages.
Above link contains many other links to other pages which contain information on gadgets.

localtime: How to tell local time in perl

localtime():
It's a function in perl which converts a time as returned by the time function to a 9-element list with the time analyzed for the local time zone. Typically used as follows:
0: sec, 1: min, 2: hour, 3:mDay, 4:mon, 5:year, 6:wDay, 7:yDay, 8:isDst

my $curTime = time();
my ( $sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime($curTime);
$year is the number of years from 1900, so for 2009 it will be 109.
so you will have to 1900 in $ year.
$year += 1900;


print "$mday/$mon/$year --- $hour:$min:$sec";

my $ltime = localtime();
print $ltime; It will print as "Thu Dec  3 00:43:57 200"

Using mkpath in perl

mkpath (path, bool, perm)

Creates a directory path and returns a list of all directories created. It requires File::Path module
It takes the following arguments:
path: Name of the path or reference to a list of paths to create.
bool : Boolean. If true, mkpath prints the name of each directory as it is created. Default is false.
perm : Numeric mode indicating the permissions to use when creating the directories. Default is 0777.
 ======================================
$path = "C:\\test" ;
mkpath($path); # it will create the directories required.
print mkpath($path, 1); # it will also print all the directories made during mkpath.

Information on Perl

If you want some more information on Perl there is one place where you can find much more on Perl, you can even join communities there on PERL. Indiastudy channel is a site which has got a lot of resources on Perl.
Check following link: http://www.indiastudychannel.com/sites/156782/ViewCommunityMembers.aspx